1. Field of Invention
The invention relates to integral blocks, chemical delivery systems and methods for delivering an ultrapure chemical from a chemical container to a point of use. In particular, the invention relates to chemical delivery systems and methods for delivering ultrapure chemicals to manufacturing process tools, such as semiconductor tools and optical fiber manufacture process tools.
2. Background of the Invention
Chemical precursors are used to grow films in the manufacturing process of integrated circuits and optical fiber products. These chemical precursors normally have ultrahigh purity levels and are fed from chemical containers to a point of use with chemical delivery systems. The chemicals could be easily contaminated if the delivery lines and those connection points are not properly purged and cleaned. Contaminants include ambient air, particulate matters, and moisture. Contaminants may also include reaction products of chemical precursors and ambient air or moisture. The contaminants may diffuse into the delivery lines from the ambient atmosphere when the lines are not properly protected. Any contaminant will seriously deteriorate the production yields. For example, particulate impurities could change the dielectric property of deposited films and short the conductive connections.
Most of the chemical precursors are delivered in liquid phase to the tools before chemical vapor deposition. Some of the chemicals are in liquid phase themselves at room condition, such as TEOS (tetraethylorthosilicate), or TiCl4.Some of the chemicals are in solid phase at low temperature and in liquid phase at an elevated temperature, such as PET (Tantalum Pentaethoxide), and TDMAT (tetrakis-dimethylamino titanium). Often, chemicals in the solid phase, such as BST (barium/strontium/titanate), are dissolved in a suitable solvent before delivery. For a stable and continuous delivery of chemicals, a dual container either in series or in parallel is usually used for delivery. An empty container could be replaced with a full container while another container is still in use. In the process of replacing an empty container, chemicals remaining inside the line and the joints must be cleaned to prevent the residue chemical from contaminating the system, or spilling into the system. Exposure to these chemicals should also be limited, as they are often extremely toxic, or pose a fire hazard or explosion risk. Another reason to clean the residual chemical is that the residuals of most precursor chemicals mentioned above will react with air and moisture. The reaction products will contaminant the delivery system and further the chemicals to be delivered. Some of the chemical may also react with air and moisture to produce solid that is very difficult to be removed. In this case, the delivery line could be blocked, resulting in discontinuation of delivery.
Therefore, when the joints of chemical container and delivery lines are disconnected, the lines must be protected from intrusion of ambient contaminates. The method to protect the lines from such an intrusion is to bleed an inert gas out of the broken joints to blank the opening. Therefore, blocking inert gas must be provided to the delivery system. After the replacement of chemical container, the lines must also be cleaned and purged with inert gas, vacuum, and in some cases with liquid solvent alternatively to assure the lines including the joints with chemical containers contaminants free.
Chemicals are usually delivered by pressurizing the chemicals with an inert gas through a manifold. When purge gas and liquid solvent are needed for system purge, a different design of manifold is commonly used. The design and operation of a delivery system vary, depending upon chemical properties. The operator has to deal with various delivery systems with different design and operation procedures. Therefore, it is not cost effective for a fab to use such delivery systems for multiple chemical precursors. Further, some necessary functions, such as bleeding gas for blanking an open joint after disconnecting a chemical container from the delivery system manifold, may not be properly arranged or may be completely ignored.
With dual or multiple containers in a parallel arrangement, the alternate usage of two or more containers indeed meets the chemical demands of process tools. It has been realized that the delivery manifold and corresponding control are more complicated than a single changeable container system. It also requires a multiple arrangement for supplying purge gas and liquid solvent. Therefore, more components such as valves and connection fittings are needed for such a delivery system. In addition, the chance for contamination of the delivery system increases because more joints need to be disconnected while replacing the empty containers.
Chemicals could have particles at rather high concentrations if the chemicals are not filtered. These particles may originate from chemical manufacturing process, chemical packaging, and transportation. Particles are contaminants and must be removed from chemicals in order to maintain chemical delivery system functioning properly and eventually high production yields of IP and optical fiber manufacture. Although there is a need to remove particles from chemicals, there are presently no satisfactory methods for doing so, because of a lack in a proper design to integrate a filtration arrangement into a chemical precursor delivery system.
In most chemical delivery systems, a relative expensive inert gas such as helium is used as the pressurization gas. In many existing chemical delivery systems, residue chemicals inside the manifold connections are purged with a same gas source as pressurization gas. Since the pressurization gas is expensive, usage of such a gas for purge purpose will increase the operation cost. Also, leakage of helium gas into the ambient atmosphere may induce operation concerns for other operation procedures. For example, chemical delivery systems or even other similar material-supplying systems need to be checked for leaking of helium from time to time. An unexpected high concentration from surrounding chemical system purge will mislead the leak check operation.
Accordingly, what is needed in the art are integral blocks and chemical delivery systems designed for delivering chemical precursors from chemical containers to a point of use. The point of use is preferably a tool for chemical vapor film deposition. In addition, the chemical delivery system would have the flexibility to easily add other function blocks. Thus, what is needed is integral blocks that can be added into the basic delivery system for various chemical delivery needs. This invention answers this need.